A semiconductor manufacturing process includes a plurality of processes, wherein a substrate supporting unit for supporting a substrate is used in processing the substrate at each process. Depending on the processing types, the substrate needs to be cooled or heated. At this time, the substrate is vacuum-adsorbed to be held on the substrate supporting unit. Since the substrate and the top surface of the substrate supporting unit are normally mirror-likely finished, the substrate is closely adhered on the top surface of the substrate supporting unit by the vacuum-adsorption, so that the temperature of the substrate can be promptly set to a predetermined level.
However, the substrate generates a large amount of heat in some processes. For example, the substrate generates a large amount of heat during, e.g., an inspection process for inspecting electric characteristics of a highly densely integrated circuit of the substrate. In this case, the substrate may not be sufficiently cooled by the substrate supporting unit. This is believed to be caused by the presence of microscopically formed fine voids due to micron-order irregularities on the substrate and the substrate supporting unit even though they are mirror-likely finished and the voids are depressurized by the vacuum adsorption to increase a contact thermal resistance.
Accordingly, there has been proposed in Japanese Patent Publication No. H8-17200 (Reference 1) and Japanese Patent No. 2536989 (Reference 2) a technology in which a liquid is supplied between the substrate and the substrate supporting unit so as to eliminate the voids therebetween to increase the cooling efficiency by using the liquid as a heat transfer medium.
In Reference 1, there is disclosed a substrate cooling system including a chuck for supporting a substrate, a source vessel for providing a liquid interface between the substrate and the chuck, and a collection vessel for collecting the liquid from the liquid interface. The top surface of the chuck has spiral grooves as a cooling circuit of a dense pitch, and an inlet and an outlet are respectively formed at both ends of the spiral grooves. The spiral grooves include three types of grooves adapted to be separately used depending on, e.g., the size of the substrate. The source vessel maintained at atmospheric pressure is connected to the inlet and the collection vessel maintained at a lower pressure than the atmospheric pressure is connected to the outlet. Further, a vacuum sealing groove is formed in the top surface of the chuck and a seal around the substrate is provided through the vacuum sealing groove. The vacuum sealing groove is configured to adsorb a peripheral portion of the substrate depending on the kinds of the substrate.
When the substrate is cooled by using the substrate cooling system, the substrate is first mounted on the chuck and is then adsorbed through the vacuum sealing groove to seal the inner side of the substrate. Subsequently, due to a pressure difference between the source vessel at the atmospheric pressure and the collection vessel at the sub-atmospheric pressure, a liquid is fed from the source vessel through the inlet into the spiral grooves and is then collected from the grooves through the outlet into the collection vessel. At this time, the liquid flows from the inlet to the outlet due to the pressure difference therebetween and, at the same time, the liquid flows across the spiral grooves due to a capillary action at the interface between the substrate and the chuck. Owing to such two actions, the entire surface of the substrate becomes wet and the liquid serves as a heat transfer medium, so that the cooling efficiency of the substrate by the chuck can be increased. Reference 2 also discloses a same technology as that in Reference 1.
In the disclosures of References 1 and 2, however, the liquid is fed from one end of the spiral grooves formed densely in the top surface of the chuck to be discharged through the other end thereof and the liquid moves across the grooves along the interface between the substrate and the chuck due to the capillary action, so that the liquid moves slowly, thus making it difficult to promptly control the temperature of the substrate.